The invention relates to a device for the treatment of water, in particular an ion exchange device for the treatment of domestic water, with means for the treatment of water, in particular an ion exchanger material with a supply container for providing a regeneration agent solution for the regeneration of the means for water treatment, in particular a brine supply container, as well as with a piston-stroke controlled metering device for the allotting of feed-water into the supply container, wherein the metering device comprises a hollow cylindrical delivery body which contains a piston which is axially displaceable and one axial surface of which faces a pressure area within the cylinder, which can be acted upon with water pressure, preferably of the water to be treated or the water which has already been treated, whereas the piston is forced in the direction of the pressure area on the side axially opposite to the pressurized area by means of a spring element, in particular a helical spring, which is supported by an end-faced inner wall of the cylinder and wherein the water volume which is displaced with a piston stroke can be fed to the supply container.
Such a device is known from DE 26 55 374 A1.
Plants or devices for the treatment of water which require a multitude of valve control processes, are driven in different ways depending on their size. Big plants, which are used for example in the industrial field, are usually equipped with a multitude of magnetic valves and have an electronic system handling the valve control program. Magnetic valves of this type are frequently too expensive for relatively small water treatment devices which are used in domestic water technology--i.e. mainly ion exchangers, however also neutralization, deferrization or demanganization filters etc. are feasible. Thus, one usually goes back to a control camshaft driven by an electromotor (see leaflet "MaBgebend in der Wasseraufbereitung" by the company JUDO Wasseraufbereitung GmbH, 01/1992, page 22) or a control cam plate, as it is known from EP 0 447 350 A2 and respectively a ceramic disc pair, known from EP 0 184 773 A2 which contains the control valves.
The electromotors used in this case, however, are relatively expensive since they have to be very robust. A further problem lies therein, to always position the control camshaft or a further control element correctly via the motor rotation, such that the right valves are opened and respectively closed at the right point in time. This can be realised for example by means of an electronically controlled stepping motor or via a positioning switch. But both possibilities are expensive. As an alternative to the electrical drive of the control elements, a drive by means of water power is possible which is considerably less expensive. For example, from U.S. Pat. No. 3,891,552, a water meter with an impeller as drive for the valve control is known, in which the mechanical control of the valve(s) is performed via the water power by means of pressurized water. A disadvantage is the expensive gear transmission for the water meter which is necessary for this valve control. A further disadvantage is the long reaction time of the water meter caused by the loss of energy due to the drive, which is approximately 150 liters per hour, whereas a conventional water meter without drive function reacts at approximately 30 liters per hour.
A further problem with the known plants for the treatment of water is the exact allotting of the regeneration agent amount. According to EP 0 347 577 B1 the measuring of the regeneration agent is performed for example via a float switch. In a method according to the above-mentioned leaflet of the company JUDO (pages 22 and 23) which is further improved thereto, fresh water is guided via the salt supply, where the fresh water becomes saturated with the regeneration salt and flows via an overflow weir into the brine provision container. Therein, it is presented for regeneration. The regeneration solution continues to flow via this weir until the floating body has reached the upper switching point of the float switch and the latter then closes the fresh water feeding valve. In this manner, a certain regeneration agent volume is metered. This method, however, has two weak points: Firstly, regeneration salt crusts may impair the mobility of the floating body and secondly there are fluctuations in the regeneration agent amount trailing across the weir in dependence upon the surface tension between the weir material and the regeneration fluid.
The two above-mentioned problems have resulted in a series of alternative methods. Thus, DE 26 44 759 A1 describes a simple water softener, in which a piston is moved by the water pressure and valves are opened and respectively closed in certain piston positions. At the same time the volume generated by the piston displacement in the guiding cylinder represents the feeding water volume and thus eventually the volume of the regeneration agent. In this connection the total allotted volume is delivered with one single stroke which necessitates a large cylinder volume.
A similar device, in which not the feeding water, but the regeneration agent directly is metered by the piston stroke, is described in DE 26 52 113 C2. In both cases a feeding with fresh water defined in terms of volume is not provided.
In contrast thereto, the initially cited DE 26 55 374 A1 describes a feeding water dosage controlled by a magnetic valve, wherein the volume control of the feeding water for the brine is performed by means of piston stroke. In the case of the known device, however, no valve control functions are provided, merely the allotting of fresh water into the brine supply container is effected.
All above-mentioned alternative devices and methods have in common that complicated regeneration methods with reduced salting, i.e. brine dilution and rewash function as well as four regenerations each day, as requested by the German Standard DIN 19636, cannot be realised. The cylinder volume, generated by the piston displacement, must also be sufficiently large such that it corresponds to the total volume of regeneration agent. A settable regeneration agent volume is realised in none of the solutions suggested in prior art and would be feasible at best by a further development of the device known from DE 26 55 374 A1, which however does not give any suggestions for a solution of the problem of valve control.